Thermal Ablation for Benign Thyroid Nodules Radiofrequency Prof Jung Hwan Baek Nguyen Van Bang INTRODUCTION Thyroid nodules: 4-8% (palpation), 10-41% (US); 50% (autopsy) Most thyroid nodules are benign Treatment: Cosmetic reasons, subjective symptoms Surgery, LT4: several drawbacks EA, PLA: some limitations Radiofrequency ablation (RFA): minimally invasive technique RFA: benign thyroid nodules / recurrent thyroid cancer RFA: Principles of Radiofrequency Ablation Refers to an alternating electric current between 200 and 1200 kHz Tissue ions are agitated by application of alternating electric current results in ion friction which creates frictional heat around the electrode Frictional heat causes significant damage in region that is close electrode Remote tumor tissue is ablated more slowly, via conductive heat RFA: Principles of Radiofrequency Ablation Dependen on both the tissue temperature achieved and the duration of heating • 40°C : no tissue damage • 42-45°C: termed hyperthermia, tissue cells to become more susceptible to damage • 46°C/ 60 or 50-52°C/4-6 : Irreversible cellular damage • 60-100°C: immediate tissue coagulation • 100-110°C: vaporization and carbonization Several factors may reduce the efficacy of RFA: temperature (vaporization/carbonization); heterogeneous nature of target tissue (fibrosis or calcification ); blood flow RFA: liver and thyroid gland Difference Thyroid gland Liver Solution Organ size Small Large Compartmentalization Tumor size Large Large Conceptual ablating unit Tumor shape Ellipsoid Round Moving shot technique Safety margin Not sufficient Sufficient Unit-by-unit ablation Depth of organ Superficial Deep Use of short and thin electrode Inclusion Criteria and Patient Preparation Inclusion criteria: subjective symptoms and/or cosmetic problems and in patients with AFTN Exclusion criteria: malignant thyroid nodules and follicular neoplasms US, US-guided FNA, appropriate laboratory tests Devices A modified, straight, internally cooled electrode (17-gauge, 15 cm in length, with a 1- 0.7- 0.5 active tip) has been used in Korea A multi-tined expandable electrode (14-gauge, 10 cm in length, with 4-9 hooks expandable to 3.5-4.0 cm) has been employed in Italy Procedures The “trans-isthmic approach method • The entire length of the electrode can be visualized on the transverse US view • Minimal exposure to the heat of the danger triangle which includes the recurrent laryngeal nerve and/or esophagus • The electrode passes through a sufficient amount of thyroid parenchyma: preventing a change in the position of the electrode tip during swallowing or talking, /preventing leakage of hot ablated fluid outside the thyroid gland Procedures The “moving shot technique” • Divide thyroid nodules into multiple small conceptual ablation units, and perform RF ablation unit-by-unit, by moving the electrode • Initially, the electrode tip is positioned in the deepest, most remote, portion of the nodule to enable the tip to be easily monitored in the absence of any disturbance caused by microbubbles 10 Follow-Up Follow-up US examinations (size, echogenicity, and intranodular vascularity) at 1, 3, 6, and 12 months, and every 6-12 months were routinely performed ... limitations Radiofrequency ablation (RFA): minimally invasive technique RFA: benign thyroid nodules / recurrent thyroid cancer RFA: Principles of Radiofrequency Ablation Refers to an alternating...2 INTRODUCTION Thyroid nodules: 4-8% (palpation), 10-41% (US); 50% (autopsy) Most thyroid nodules are benign Treatment: Cosmetic reasons, subjective symptoms... gland Procedures The “moving shot technique” • Divide thyroid nodules into multiple small conceptual ablation units, and perform RF ablation unit-by-unit, by moving the electrode • Initially,